G’day everyone, I hope this is the correct place to ask this sort of question, I’m still quite new to Python. Using OpenCV2, I can stream and write a video file from my webcam… I’d like to take this a step further, ideally by having a continuous video buffer (let’s say 1minute), and after an event…

Yes, it’s definitely possible! But rather than recreating it from scratch, I would recommend looking into OBS Studio. It has a “replay buffer” concept that is pretty much exactly what you’re talking about, and you can signal it to save that buffer as a video file, while continuing to record to the b…

G’day Chris, Thanks for your reply. I hadn’t considered offloading the video stream to another process, it’s not a bad idea and would save on my coding, but it might affect portability. Something I’ll need to take into account is this will end up on a headless server (something similar to a Jetso…

Can you do it frame-by-frame? import cv2 capture = cv2.VideoCapture(...) frames = [] while True: ret, frame = capture.read() frames.append(frame) if too_many_frames(): frames.pop(0) if special_user_event(): capture_one_more_minute_of_frames() write_to_disk(fr…

[image] Brad: Something I’ll need to take into account is this will end up on a headless server (something similar to a Jetson Nano or Raspberry Pi4… I’ve got a few old boards stashed away in a draw). Whatever the video streaming service I use would need to operate without a local user logging i…

I’ve been doing more reading today and came past the term “Ring Buffer” which I believe is the same concept you’re describing. It doesn’t need to be exact, it’s just for reviewing purposes… this will mean later I won’t need to parse through hours of video looking for what I’m after :slight_smile: I…

[image] Brad: I’ve been doing more reading today and came past the term “Ring Buffer” which I believe is the same concept you’re describing. It doesn’t need to be exact, it’s just for reviewing purposes… this will mean later I won’t need to parse through hours of video looking for what I’m after…

You make it look so easy :slight_smile: LOL Originally I was thinking along very similar lines, just didn’t know how to implement the logic. I’ve recently discovered the concept of a “ring buffer” which seems more flexible in my situation, but I really do appreciate the time put into responding

Ahhh, yes… I read that certain formats of video couldn’t be joined in sections (something about mp4 can’t, MTS can…?) I’ll make sure I pay attention to that so I don’t get caught out.

Yep. I’d advise giving this page a read: https://trac.ffmpeg.org/wiki/Concatenate#protocol And then doing some experimentation.

OpenCV2 - Constant video stream, write file 1 minute before and after an event

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Rosuav (Chris Angelico) August 28, 2023, 9:17am 7

Yes, exactly!

That sounds like a pretty decent plan. The choice of file format (and specifically video encoding) for the ring buffer has to strike a balance between file size, quality, and ability to concatenate sections conveniently.